This indicates an attack attempt against an Information Disclosure vulnerability in WebRTC.
The vulnerability is caused by a design error in the application. A remote attacker can disclose users' local and public IP addresses via a crafted web page.
WebRTC 1.0 on Google Chrome
WebRTC 1.0 on Mozilla Firefox
Information Disclosure: Remote attacker can gain sensitive information from vulnerable systems.
Currently we are unaware of any vendor supplied patch for this issue.